Conventionally, mobile telephones are a known form of mobile communication terminal. With mobile phones, in particular, IMT-2000 mobile phones perform communication using an IC card called a SIM (Subscriber Identity Module) card.
Each SIM card stores a subscriber identifier such as a telephone (subscriber) number or a carrier (contracted company and the communication scheme thereof) for every line contract. When a user makes contract with a carrier, the user is provided with a SIM card. Mounting this SIM card in a phone and reading out an identifier from the SIM card enables calls to be made and taken. Also, interchanging the SIM card for mounting in a phone enables a plurality of phones to be used for different purposes using a single contracted line.
In the case where a single user contracts a plurality of communication lines, SIM cards storing an identifier for every contract are provided. Therefore, interchanging the SIM cards for mounting in a phone enables a plurality of lines to be used for different purposes with the one phone. For example, a plurality of lines can alternatively be used for business and private purposes.
A phone capable of mounting two SIM cards has also been proposed (e.g., see Japanese Patent Application Laid-Open No. 2003-189361). Therefore, mounting the two SIM cards provided as a result of a user contracting two different carriers enables calls to be made using these two carriers with the one phone.
If only one line is used, only functions and operation screens tailored to the contracted line need be displayed.
However, in the case of a phone capable of using a plurality of lines, the user needs to designate the carrier to be used when the user makes a call.
Therefore, the user needs to designate the carrier to be used every time they make a call, which is cumbersome, thus problematic